a. Field of the Invention
The present invention relates to a method of obtaining lupulin-rich products from hops, and particularly it relates to a method comprising a step of subjecting hop cones in the frozen state to coarse crushing and sieving the thus crushed hops thereby to obtain a lot of hops with high concentration of lupulin as accumulated beneath sieves, and a step of recrushing the portion which passed over the screen in the foregoing step into finer fragments and sieving the thus recrushed hops thereby to obtain another lot of hops rich in lupulin as accumulated beneath the sieve.
B. Description of the Prior Art
As is well known, hops are indispensable for the purpose of imparting the characteristic aroma and bitter taste to beer, ale and other brewed beverages. The term hop means the mature cone of the female flower of a plant belonging to mulberry. The substance to which the characteristic aroma and bitter taste are attributable is contained in the lupulin gland which grows at the base of bracteoles and stipular bracts or ovaries when the cone ripens; other portions of bracts or portions of stalks do not contain any contributive ingredients. Brewing of beer and the like is performed throughout the year, while the harvest of hops is seasonally limited. Therefore, it is necessary to preserve hops over a long period of time, so that there are required large size storage equipment as well as the greatest circumspection to prevent change in quality. As the countermeasures, there have been proposed and put into practice some methods of concentrating lupulin by processing hops to divide them into portions rich in lupulin and portions not containing lupulin. For example, in U.S. Pat. No. 2,833,652 there is disclosed a method of subjecting lupulin to freezing, coarse crushing and thereafter sieving. According to this method, however, the crushing is carried out relatively coarsely, and therefore, although a concentration of lupulin can be effected, the volume of yield is not satisfactory. Besides, the method in this U.S. Pat. seems to be based on experiments conducted by using mainly fresh hops; but the hops to be dealt with in general hop manufactories are dry hops, so that this method is not apposite as regards the dry hops. Granting that the method of this U.S. Pat. does not exclude the processing of dry hops, yet no particular descriptions thereof have been made therein. Meanwhile, with a view to increasing the yield of concentrated hop and degree of concentration, a method of subjecting hops in the frozen state to crushing into fragments finer than that in the foregoing method of U.S. Pat., followed by sieving has been disclosed in German Pat. No. 1,234,656: however, when hops are crushed to such extent of fineness as is taught therein, the lupulin-rich portions and the crushed bracts as well as the stalks are fairly approximate in gravity, so that it is infeasible to achieve a sufficient separation effect by blow-sifting or sieving. And, in order to increase the volume of yield, sieving must be conducted repeatedly. Besides, when increase of the volume of yield is attempted, the degree of concentration will decrease.